1. Field of the Invention
The present invention relates to a light emitting unit, an apparatus and method for manufacturing the same, an apparatus for molding a lens thereof, and a light emitting device package thereof, and more particularly, to a light emitting unit, an apparatus and method for manufacturing the same, an apparatus for molding a lens thereof, and a light emitting device package thereof which are capable of achieving an enhancement in light extraction efficiency and an improvement in mass productivity.
2. Discussion of the Related Art
Generally, liquid crystal display (LCD) devices, which are a kind of light reception type flat display, have no ability to emit light by itself. For this reason, such an LCD device forms an image by selectively transmitting illumination light irradiated from the external of the LCD device. To this end, a light source must be arranged at the back side of the LCD device, in order to illuminate the LCD device. This light source is called a “backlight unit (BLU)”.
Such a backlight unit must uniformly irradiate light over the overall surface of a liquid crystal panel. To this end, where light emitting diodes (LEDs) are used for light emitters of the backlight unit, it is necessary to arrange a lens on a package of each LED, in order to obtain a uniform brightness distribution of illumination light.
For an example of a method for installing a lens on an LED package, there is a method in which a lens is injection-molded using an epoxy resin or polycarbonate (PC)-based resin, and the molded lens is attached to an LED package.
The attachment of the lens to the LED package may be achieved using a method shown in FIG. 1. That is, as shown in FIG. 1, an encapsulate material 11 is filled in a region defined over an LED 12 of an LED package 10, and a lens 20 is then attached to an upper surface of the LED package 10 filled with the encapsulate material 11.
In this case, for the encapsulate material 11 of the LED package 10, a material such as silicon is used. However, when the lens 20, which is made of an epoxy resin or a PC-based material, is attached to the encapsulate material 11 which is a silicon, the following problems may occur.
First, when the lens 20 is made of an epoxy resin, it has no bonding force to silicon, which is used for the encapsulate material 11. For this reason, an air layer is formed between the two materials.
When an air layer is formed between the two materials, as mentioned above, light may be totally reflected while passing through the silicon encapsulate material 11 and the epoxy resin lens 20. As a result, a part of light emerging from the LED 12 cannot directly reach the lens 20.
Since the light travels along a complex path between the encapsulate material 11 and the lens 20 due to such a total reflection phenomenon, the number of light beams finally emerging out of the LED package 10 is reduced. As a result, a reduction in light amount occurs. For this reason, practically, a degradation in brightness occurs.
Furthermore, when the epoxy resin used for the lens 20 is exposed to a high temperature condition for a prolonged period of time, a yellowing phenomenon may occur. For this reason, when the lens 20 may be discolored in the manufacture thereof, so that it may function as a main factor of a degradation in light amount.
Second, when the lens 20 is injection-molded using a PC-based resin, interfaces are formed between the silicon encapsulate material 11 and the PC lens 20, similarly to the former case. Due to a full reflection phenomenon occurring at the interfaces, a degradation in the light amount of the LED package 10 may occur.
Meanwhile, in the case of a modulized LED package, it is generally formed using a reflow process. A temperature increase to about 270° C. may occur during the reflow process.
However, in association with the PC lens 20, there is a difficulty in executing the reflow process. This is because the material of the PC lens 20 is a thermoplastic resin, so that the PC lens 20 may be deformed at a temperature of 160° C. or more due to melting thereof.